Vehicles commonly have a key cylinder (lock body) to prevent drivers from removing the vehicle's ignition key while the vehicle is running and while the transmission is shifted out of the park position. The key cylinder can turn to several positions while the vehicle's ignition key is in the key cylinder, for example, “lock,” “acc,” “on,” and “start.” The key cylinder prevents the key from being removed while the key cylinder is in any position other than the “lock” position.
Modern vehicles also have a brake transmission shift interlock (BTSI) that interacts with the vehicle's shift lever. BTSIs prevent the driver from shifting the transmission out of the park position unless the vehicle brake is applied.